The present invention relates to a wand which can read optically the value of bar code printed in packing of the goods, more particularly, having structure of variable resolution.
Hithertofore there have been known various types of wands which extract the information that is optically encoded in the bar code symbol and convert it into the character data representation of the symbol's code.
One known type of such wand is of the reflective optical sensor type as shown in FIG. 5 in which a light beam radiated from a light emitting diode (LED) is focused by a lens, and illuminated on the surface of bar code area. After the light reflected back from the surface of bar code area is focused by another lens, the reflected light signal is converted to electrical signal by a detector, such as a photodiode or a phototransister, then the electrical signal is transmitted to an attached decoder, or other processing apparatus.
Another known type is of the receiver lens type as shown in FIG. 6, wherein a light beam radiated from at least one light emitting diode without focusing the light is illuminated on the surface of bar code area, and then the light reflected back from the surface of bar code area is focused only at light receiving portion and sensed by the detector through a slit.
Among other known wands there has been used an optical fiber receiver type as shown in FIG. 7, wherein the light beam radiated from a LED is focused by using a ball lens or any other optical system, and then the light reflected back from the surface of bar code area is sensed at the light receiving portion by using an optical fiber.
However, in the above described conventional wands, the lenses of the light transmitting portion and the light receiving portion are usually fixed, therefore, the light detectabilities and the resolutions of the wands are fixed according to the optical system characteristics.
In the case of the optical fiber receiver type, the resolution and the detection distance are determined by the spot size of the focused light and NA (numerical aperture) value of the optical fiber, so that there is the drawback that the light detectability and the detection distance are fixed. Accordingly, this inherent nature make the resolutions of the wands to be fixed and there are disadvantages that the economical efficiency and the operational efficiency are got worse because the users should prepare various kinds of wands in accordance with the bar code densities.